This invention relates to a fixing apparatus for use in an image forming apparatus such as a copying machine, a printer, and a FAX machine, and in particular, to a fixing apparatus capable of making a quick start.
Heretofore, for a fixing apparatus for use in an image forming apparatus such as a copying machine, a printer, and a FAX machine, a fixing method using a heat roller has been adopted widely from low-speed machines to high-speed machines and from monochromatic machines to full-color machines as a method which has a high degree of technological completion and stability.
However, in a fixing apparatus of the conventional fixing method using a heat roller, there is a problem that, because it is necessary to heat a heat roller having a large heat capacity in heating a transfer material and toner particles, the method is not advantageous from the view point of economizing energy, and further, it takes a long time for the machine to warm up the fixing apparatus at the time of printing, which makes the printing time (warm-up time) long.
In order to solve this problem, it has been proposed and put into practice recently a fixing apparatus or an image forming apparatus using the fixing apparatus of a type of film fixing method, in which the heat roller is substituted by a heat fixing film (film for heat fixing) having an ultimately small thickness to make the heat capacity small, and the efficiency of heat transfer is raise to a large degree by bringing a temperature-controlled heater (a ceramic heater) in direct pressing contact with the heat fixing film, to make a quick start which economizes energy and requires almost no warm-up time.
Further, it has been disclosed in the publications of unexamined patent application S52-106741, S57-82240, S57-102736, S57-102741, etc., a fixing method in which no warmup time is required and a quick start is aimed at, by using a ray-transmitting base member as a modification of a heat roller for a ray fixing roller (a rotary member for applying heat) and irradiating toner particles by heat rays from a halogen lamp (ray-radiating device for radiating heat rays) provided inside to fix them by heating. Further, it has been disclosed in the publication of an unexamined patent application S59-65867, a fixing method in which a ray-absorbing layer for generating heat (heat ray absorbing layer) is provided on the outer circumferential surface of a ray-transmitting base member to make up a ray fixing roller (rotary member for applying heat), and rays from a halogen lamp (ray-radiating device for radiating heat rays) are made to be absorbed by the ray absorbing layer provided on the outer circumferential surface of the ray-transmitting base member, to fix a toner image by the heat of the ray-absorbing layer for generating heat.
In the fixing apparatus disclosed in the above-mentioned publications of the unexamined patent application S52-106741 etc., the economizing of energy and a quick start with a shortened warm-up time are aimed at by the methods in which toner particles are heated and fixed by applying heat rays from a halogen lamp (ray-radiating device for radiating heat rays) through a ray-transmitting base member, and in the fixing apparatus disclosed in the above-mentioned publication of an unexamined patent application S59-65867, by the methods in which ray absorbing layer for generating heat (heat ray absorbing layer) is provided on the outer circumferential surface of a ray-transmitting base member to make up a ray fixing roller (rotary member for applying heat), and heat rays from a halogen lamp (ray radiating device for radiating heat rays) are applied through the ray-transmitting base member, to fix toner particles by the heat of said heat ray absorbing layer; however, because the fixing ability of the above-mentioned methods is poor, the inventors of this application have proposed it in the publication of an unexamined patent application H11-327341, a fixing apparatus by which a quick start is enabled and fixing ability for a toner image is improved by providing a ray-transmitting elastic layer or a ray-transmitting heat insulating layer made of a rubber material between the ray-transmitting base member and the ray absorbing layer for generating heat (heat ray absorbing layer) to form a ray fixing roller made up of a soft roller.
However, in the fixing apparatus of the above-mentioned proposition, the ray-transmitting base member which is provided in the rotary member for applying heat and is mainly made of a glass material has a poor cylindricity and roundness, has an uneven thickness, and also has an unevenness of thickness produced in the ray-transmitting elastic layer or the ray-transmitting heat insulating layer provided on the outside (outer circumferential surface) of the ray-transmitting base member, which makes non-uniform the temperature distribution inside the rotary member for applying heat with respect to the direction along the circumferential surface and makes non-uniform the radiation quantity reaching the heat ray absorbing layer at the surface; therefore, the unevenness of heat generation in the heat ray absorbing layer at the surface is produced, and it occurs a problem that the temperature of the heat ray absorbing layer is unstable and non-uniform.
It is an object of this invention, by solving the above-mentioned problem, to provide a fixing apparatus capable of making a quick start, wherein the temperature distribution inside the rotary member for applying heat is made uniform by preventing the unevenness of heat generation in the ray-transmitting base member and ray-transmitting elastic layer or ray-transmitting heat insulating layer inside the rotary member for applying heat, and the temperature of the heat ray absorbing layer is made stable and uniform by preventing the unevenness of heat generation in the heat ray absorbing layer at the surface.
The above-mentioned object is accomplished by a fixing apparatus for fixing a toner image on a transfer material by applying heat and pressure onto said transfer material comprising a ray radiating device for radiating heat rays inside, and being provided with a cylindrical ray-transmitting base member having transmittance for said heat rays, a cylindrical ray-transmitting elastic layer or ray-transmitting heat insulating layer having transmittance for said heat rays, and a heat ray absorbing layer for absorbing said heat rays outside said ray-transmitting elastic layer or said ray-transmitting heat insulating layer to form a roll-shaped rotary member for applying heat, wherein, in the case where the fluctuation of the thickness of said ray-transmitting base member and the fluctuation of the thickness of said ray-transmitting elastic layer or said ray-transmitting heat insulating layer are both equal to or larger than 0.1 mm, the difference between the heat ray absorbing ratio (%) per unit thickness (mm) in said ray-transmitting base member as a single layer and the heat ray absorbing ratio (%) per unit thickness (mm) in said ray-transmitting elastic layer or said ray-transmitting heat insulating layer as a single layer is made equal to or less than 20%.